1. Field of the Invention
The present invention relates to a transmission control apparatus that controls a transmission mounted in a vehicle and particularly to improvement of a plurality of linear solenoids that generate adjustment hydraulic pressure outputs corresponding to supply currents in a transmission control apparatus, improvement of a supply current control apparatus for the linear solenoid, and an adjustment method for output characteristic of the transmission control apparatus.
2. Description of the Related Art
As is well known, a transmission control apparatus for determining the transmission gear ratio of a transmission mounted in a vehicle includes a plurality of linear solenoids that is selectively supplied with a current in accordance with the selection position of the gearshift lever, the vehicle speed, and the accelerator-pedal depressing degree and generates an adjustment hydraulic pressure output corresponding to the supply current, for the purpose of determining the transmission gear ratio; and a supply current control apparatus that controls the supply current for the linear solenoid.
Because a transmission control apparatus for determining the transmission gear ratio of a vehicle transmission needs to be adjusted in the combination with a plurality of linear solenoids incorporated in the transmission, it is configured as a system inseparably integrated with the transmission; i.e., there is established electromechanical integration in which the transmission control apparatus and the transmission are combined with each other. Patent Document 1 describes that in a transmission control apparatus cited as an example of conventional apparatus and illustrated in FIGS. 16A and 16B, an electronic control unit 122, which is a centralized control apparatus for collectively controlling a plurality of linear solenoids 121, is configured with a microcomputer 123, a plurality of linear solenoids, and a plurality of drive control apparatuses 124 that correspond to the respective linear solenoids 121, and for the purpose of performing thermal correction for a linear solenoid 121 having temperature dependency, the characteristic parameters of the corresponding drive control apparatus 124 are adjusted in the production step for a transmission.
In FIG. 6 of Patent Document 1, there is provided a plurality of linear solenoid modules 1 that are each configured by integrating a linear solenoid 3 and a linear solenoid control circuit 4, and the linear solenoid control circuits 4, which are distributed control apparatuses in the respective linear solenoid modules 1, are connected with the respective output ports of a single microprocessor 63 in an electronic control unit 62. In each of the production steps for the linear solenoid modules 1, characteristic adjustment parameters at a time when the integrated linear solenoid 3 and linear solenoid control circuit 4 are combined with each other are written in a characteristic parameter storage device 6 (refer to FIG. 1 of Patent Document 1) in the linear solenoid control circuit 4. As a result, in the production step for the transmission, it is not required to adjust the characteristic parameters for each combination of the linear solenoid 3 and the linear solenoid control circuit 4.
In contrast, FIGS. 1 and 9 in Patent Document 2 discloses a flow-rate control apparatus in which for accurately controlling the flow rate of a pressure fluid that flows out from each of orifices 48a through 48c selected by on/off valves 46a through 46c, a linear solenoid valve 64 and a pressure sensor 78 are provided at upstream positions, the upstream pressure corresponding to the effective cross-sectional area of the selected orifice is set, a controller controls the excitation current for the linear solenoid 64 in such a way that the set upstream pressure and the detected pressure detected by the pressure sensor 78 coincide with each other.